1. Field of the Invention
The present invention relates to a treatment solution for manufacturing a semiconductor and a method of manufacturing a semiconductor using the same. In particular, the invention relates to a pre-strip treatment step before stripping a patterned photoresist which has been used for forming a metal interconnect layer, and a method of manufacturing a semiconductor device using the above solution and method.
2. Description of the Related Art
In a typical semiconductor manufacturing process, photolithographic processes are used to form features such as interconnects. Photolithographic processes utilize photoresist materials to imprint the patterns required to form interconnects or other features. As part of the manufacturing process, it is necessary to periodically remove photoresist residue, as well as other residues and contaminants such as byproducts from etching reaction, which often accumulate on the sidewalls of a raised feature, and reaction residue from plasma processes.
To achieve faster operating speeds in semiconductor devices, higher levels of the integration, and therefore finer patterning is required. Thus, cleaning processes become more important for example after dry etching using a photoresist to form metal interconnects or a contact hole for connecting metal interconnects to each other.
In a current semiconductor fabrication process, conductive layers are formed of various kinds of metals, metallized materials and alloys. Vias or contacts are formed for interconnecting lower and upper conductive layers. The vias are mainly formed of tungsten (W). For example, a via hole is opened over a lower interconnect and filled with tungsten to connect the lower interconnect to an upper interconnect.
FIGS. 1 through 3 are cross-sectional views illustrating the steps for forming metal interconnects on a semiconductor substrate 10 using a typical method.
Referring to FIG. 1, an interlayer insulating film 14 having a via hole H1 exposing a part of a lower interconnect layer 12 is formed on a semiconductor substrate 10 on which the lower interconnect layer 12 made of aluminum (Al) or aluminum alloys is formed. Then, the via hole H1 is filled with tungsten, thus forming a contact 20. A metal layer 22 made of aluminum or aluminum alloys is deposited over the contact 20.
Referring to FIG. 2, desired photoresist pattern 32 is formed on the metal layer 22 to define an upper interconnect layer which is to be connected to the lower interconnect layer 12 via the contact 20. However, when an overlap margin is insufficient as a result of the integration of a semiconductor device, a photoresist pattern 34 having an incorrect width may result, even though a process for forming the desired photoresist pattern 32 is performed.
FIGS. 3, 4A and 6B illustrates the resultant structure formed by dry etching the metal layer 22 using the photoresist pattern 34. As shown in FIG. 3, after the metal layer 22 is patterned using the photoresist pattern 34, an upper interconnect layer 22a is obtained, and simultaneously a part of the contact 20 is exposed.
At this time, the exposed portion of contact 20 is severely damaged during the dry etching process for patterning the upper interconnect layer 22a. When a stripping process is then performed to remove the photoresist pattern 34, a part or all of the tungsten contact 20 is also removed as shown in FIG. 4B.
Consequently, a complete tungsten plug does not exist in the via hole H1, or so that a complete electrical contact is not formed between the lower and upper interconnect layers 12 and 22a. 
If contact 20 is damaged as described, the semiconductor device will likely operate as designed and the process yield is significantly decreased.
To solve the above problems, it is an object of the present invention to provide a photoresist pre-strip treatment solution which can prevent an exposed metal contact from being damaged during stripping of a photoresist after dry etching a metal interconnect layer.
It is another object of the present invention to provide a method of removing a photoresist by which an exposed metal at a via is protected.
It is still another objective of the present invention to provide a method of fabricating a semiconductor device, by which metal interconnects can be effectively and reliably connected to each other.
Accordingly, to achieve the first objective, a pre-stripping treatment solution is provided in which an organic acid solution having a carboxyl group is mixed with deionized water at a volume ratio of 1:0 to 1:100. Preferably, in the photoresist pre-strip treatment solution, the organic acid solution and the deionized water are mixed at a volume ratio of between 1:5 and 1:20.
The organic acid solution is a solution selected from the group consisting of an acetic acid solution and a citric acid solution. The acetic acid solution contains acetic acid of 50 to 99.9% by weight.
To achieve the second objective, there is provided a method of removing a photoresist used as a dry etch mask. In this method, the photoresist is ashed. The resultant structure is treated with a pre-stripping treatment solution as described above. The photoresist is then stripped using a cleaning solution according to known methods.
To achieve the third objective, a method of manufacturing a semiconductor device is provided. In this method, a first conductive layer of a metal such as Al, Cu, Pt or metal alloys is formed on a semiconductor substrate. An interlayer insulating film is then formed over the first conductive layer. The interlayer insulating film is patterned with a photoresist, and then dry etched to form a hole and expose the first conductive layer. The photoresist pattern is ashed. The resultant structure is treated using a pre-stripping treatment solution as described above. The photoresist pattern is then stripped using well-known cleaning solutions.
After the photoresist pattern has been stripped, a contact plug is formed by filling the hole with a metal such as tungsten or metal silicide. A second conductive layer covering the upper surfaces of the interlayer insulating film and the contact plug is then formed of aluminum, copper, platinum or metal alloys. The second conductive layer is patterned with photoresist, and dry etched to form a second patterned conductive layer. The second photoresist pattern is ashed. The resultant structure is treated with a pre-stripping treatment solution as described above. The second photoresist pattern is stripped by well-known methods. According to the present invention, the metal contact can be protected during stripping of the photoresist material.